Soft paintable polymer composition

ABSTRACT

A soft paintable polymer composition comprising: 
     (a) from 0 to about 90 parts by weight (pbw) of a hydrogenated block copolymer comprised of at least one vinyl aromatic hydrocarbon and at least one conjugated diene, 
     (b) from about 10 to about 100 pbw of a functionalized hydrogenated block copolymer comprised of at least one vinyl aromatic hydrocarbon and at least one conjugated diene, wherein (a) and (b) must add up to 100 pbw, 
     (c) from about 50 to about 300 pbw of a predominantly aliphatic hydrocarbon processing oil, and 
     (d) from about 5 to about 150 pbw of a polyolefin.

BACKGROUND OF THE INVENTION

This invention relates to polymer compositions containing hydrogenatedblock copolymers of vinyl aromatic hydrocarbons and conjugated dienes,processing oils and polyolefins. More particularly, the presentinvention relates to such polymers which are made both soft andpaintable.

Polymer compositions containing the above block copolymers, processingoils and polyolefins are well known. They usually additionally comprisea filler compound. Such compositions have been used in the automotiveindustry for molded parts such as grommets, sound barriers and airducts. However, these compositions are relatively hard and are not easyto paint with polyurethane-based paints. Since these compositions dohave other advantages, such as very good low temperature brittleness,which make them quite useful in many applications, including automotiveapplications, it would be a distinct advantage if a way could be foundto make such compositions paintable and soft so that they could be usedin the manufacture of padded car door parts, arm rests and othermaterials which require the combined characteristics of such polymersincluding flexibility, excellent resistance to ozone, UV radiation andweather, good heat and chemical resistance and are easily processable.The advantages of such compositions are described in "AutomotiveApplications of Styrenic Thermoplastic Elastomers" by Geoffrey Holdenand Kyle H. Speer, Automotive Polymers and Design, 58, No. 3, February1989.

In many automotive interior applications, there is a need for parts witha rigid substructure and a soft surface. Some examples are steeringwheels, instrument panels, air bag doors and consoles. Such parts can beboth functionally and aesthetically effective. Functionally, they canserve to reduce injuries caused by collisions. Aesthetically, they givea more attractive appearance and luxurious feel to the interior, whichmany buyers prefer to the current systems. For both these reasons, theuse of soft surfaces molded over a rigid substructure is growing.

SUMMARY OF THE INVENTION

The present invention renders the above-described polymer compositionspaintable with polyurethane paints which is currently not possible. Inaddition, the present invention creates soft paintable polymers whichare useful for dashboards, door panels, consoles, air-bag doors, glovecompartment doors and the like.

The soft paintable polymer composition of the present inventioncomprises from 0 to about 90 parts by weight (pbw) of a hydrogenatedblock copolymer comprised of at least one vinyl aromatic hydrocarbon andat least one conjugated diene, from about 10 to about 100 pbw of afunctionalized hydrogenated block copolymer of at least one vinylaromatic hydrocarbon and at least one conjugated diene, wherein thetotal amount of the two block copolymers must add up to 100 pbw. Thecomposition also comprises from about 50 to about 300 pbw of apredominantly aliphatic hydrocarbon processing oil and from about 5 toabout 150 pbw of a polyolefin. In the most preferred embodiment, theblock copolymer is functionalized by grafting maleic acid or maleicanhydride onto the conjugated diene block after hydrogenation.

DETAILED DESCRIPTION OF THE INVENTION

The base polymers of the present invention are block copolymers ofconjugated dienes and vinyl aromatic hydrocarbons. Such block copolymersmay be multiblock copolymers of varying structures containing variousratios of conjugated dienes to vinyl aromatic hydrocarbons includingthose containing up to about 50% by weight of vinyl aromatichydrocarbon. Thus, multiblock copolymers may be utilized which arelinear or radial, symmetric or asymmetric, and which have structuresrepresented by the formulae, A-B, A-B-A, A-B-A-B, B-A, B-A-B, B-A-B-A,(A-B)₀,1,2, . . . B-A and the like wherein A is a polymer block of avinyl aromatic hydrocarbon and B is a polymer block of a conjugateddiene that has been hydrogenated.

The block copolymers may be produced by any well known blockpolymerization or copolymerization procedures including the well-knownsequential addition of monomer techniques, incremental addition ofmonomer technique or coupling technique as illustrated in, for example,U.S. Pat. Nos. 3,251,905, 3,390,207, 3,598,887 and 4,219,627 which areherein incorporated by reference. As is well known in the blockcopolymer art, tapered copolymer blocks can be incorporated in themultiblock copolymer by copolymerizing a mixture of conjugated diene andvinyl aromatic hydrocarbon monomers utilizing the difference in theircopolymerization reactivity rates. Various patents describe theappropriation of multiblock copolymers containing tapered copolymerblocks including U.S. Pat. Nos. 3,251,905, 3,265,765, 3,639,521 and4,208,356 which are herein incorporated by reference.

Conjugated dienes which may be utilized to prepare the polymers andcopolymers include those having from 4 to 8 carbon atoms and alsoinclude 1,3-butadiene, 2-methyl-1,3-butadiene(isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like. Mixtures ofsuch conjugated dienes may also be used. The preferred conjugated dienesare 1,3-butadiene and isoprene.

Vinyl aromatic hydrocarbons which may be utilized to prepare copolymersinclude styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene,1,3-dimethylstyrene, alpha-methylstyrene, vinylnapthalene,vinylanthracene and the like. The preferred vinyl aromatic hydrocarbonis styrene.

While these block copolymers have a number of outstanding technicaladvantages, one of their principle limitations lies in their sensitivityto oxidation. This can be minimized by hydrogenating the copolymers,especially in the diene blocks. The hydrogenation of these polymers andcopolymers may be carried out by a variety of well established processesincluding hydrogenation in the presence of such catalysts as RaneyNickel, noble metals such as platinum, palladium and the like andsoluble transition metal catalysts. Titanium biscyclopentadienylcatalysts may also be used. Suitable hydrogenation processes which canbe used are ones wherein the diene-containing polymer or copolymer isdissolved in an inert hydrocarbon diluent such as cyclohexane andhydrogenated by reaction with hydrogen in the presence of a solublehydrogenation catalyst. Such processes are disclosed in U.S. Pat. Nos.3,113,986, 4,226,952 and Re. 27,145, the disclosures of which are hereinincorporated by reference. The polymers are hydrogenated in such amanner as to produce hydrogenated polymers having a residualunsaturation content in the polydiene block of less than about 20%, andpreferably as close to zero percent as possible, of their originalunsaturation content prior to hydrogenation.

The base polymer may be used in an amount up to 90% of the total amountof functionalized and unfunctionalized polymer present in thecomposition or it may not be used at all. It is preferred that the basepolymer be used in an amount from about 50% to about 90% of the totalamount of functionalized and unfunctionalized block copolymer present inthe composition. One reason why it is preferred to use unfunctionalizedblock copolymer is that it is less expensive than functionalized blockcopolymer. If less than about 50% of the unfunctionalized polymer isused, then the total cost of the product may be uneconomic and if morethan about 90% of this polymer is used then there may be insufficientfunctionality to achieve the desired effect. It is preferred that thispolymer be relatively high in molecular weight because such polymershave better upper service temperatures, i.e. they resist distortion athigher temperatures better than lower molecular weight polymers.

In general, any materials having the ability to react with the basepolymer are operable for purposes of the present invention to make thefunctionalized polymers used herein. In order to incorporate functionalgroups into the base polymer, monomers capable of reacting with the basepolymer, for example, in solution or in the melt by free radicalmechanisms or other are necessary. Monomers may be polymerizable ornonpolymerizable. However, preferred monomers are nonpolymerizable orslowly polymerizable.

The functionalized block copolymers of the present invention arehydrogenated block copolymers as described above which have beenfunctionalized, i.e. reacted with various functional groups. Among thefunctional groups which may be reacted with such block copolymers toproduce a functionalized block copolymer useful in the present inventionare acid or anhydride groups or derivatives thereof which are graftedonto a conjugated diene block, carboxyl groups which are added onto thevinyl aromatic hydrocarbon blocks, sulfonate groups, alcohol groups,imides, acid chlorides, aldehydes, amines, amides, epoxy groups,isocyanates and esters. Functionalized polymers containing carboxylgroups reacted onto the vinyl aromatic hydrocarbon block are describedin U.S. Pat. No. 4,868,245 which is herein incorporated by reference.Functionalized polymers incorporating sulfonate groups into the polymerare described in commonly assigned copending application "SulfonatedBlock Copolymers", Ser. No. 198,543, filed May 24, 1988.

The preferred monomers for functionalizing the polymers of the presentinvention are those which can be grafted onto the polymer in freeradical initiated reactions. Such preferred polymers include acids oranhydrides or derivatives thereof such as carboxylic acid groups andtheir salts, anhydrides, esters, imide groups, amide groups, acidchlorides and the like. Such monomers and functionalized polymersincorporating them are described in U.S. Pat. No. 4,578,429 which isherein incorporated by reference. The preferred modifying monomers areunsaturated mono- and polycarboxylic-containing acids and anhydrides andother derivatives thereof. Examples of such monomers include maleicacid, maleic anhydride, fumaric acid and the other materials mentionedin the above-referenced patent.

The functionalized copolymers of the present invention must comprise atleast about 10% of the total amount of the block copolymers in thecomposition in order to achieve the advantages of the present invention,i.e., in order to render the compositions sufficiently paintable bypolyurethane based paints. If less than 10% is used, then thefunctionality of the final product may be insufficient to give goodpaint adhesion. The functionalized block copolymer may comprise up to100% of the block copolymer in the composition. However, it is preferredthat the functionalized block copolymer comprise from about 10% to about50% of the total amount of block copolymer in the composition becausethe functionalized polymers are often of low molecular weight and sogive products with poor upper service temperatures if large amounts areused.

The composition must contain a hydrocarbon processing oil which ispredominantly aliphatic in nature in order to make the compositionsufficiently soft for the uses intended, i.e., door panels, dashboards,consoles, map pocket covers, seatbacks, air bag doors, etc. Assumingthat the total amount of block copolymer is 100 parts by weight, theprocessing oil is present in the composition in an amount from about 50to about 300 parts by weight. If less than 50 parts by weight is used,then the composition will be too hard and if more than about 300 partsby weight are used, then the oil may bleed out. It is preferred that theamount of oil present range from about 150 to about 250 parts by weightbecause this range has been found to give products in the requiredhardness range. It is preferred that the hydrocarbon processing oil havea low volatiles content because oil that volatilizes will cause"fogging" on the automobile glass surface.

A polyolefin is required to be included in the composition of thepresent invention so that the composition can be injection moldedeasily. We theorize that it performs this function in the melt by actingas a second phase that is swollen by some of the oil. It also improvesupper service temperature and solvent resistance. Polypropylene is thepreferred polyolefin for use in the present invention, but otherpolyolefins such as polyethylene, poly-4-1-methylpentene and otherscould be used and also blends of such polyolefins could be used.

The polyolefin may be present in an amount from about 5 to about 150parts by weight, assuming that the total amount of block copolymer is100 parts by weight. If less than about 5 parts by weight is used, thenthe composition will be difficult to injection mold because the amountof the second phase will be insufficient to enhance moldability. If morethan about 150 parts by weight is used, then the composition will be toohard for the intended use. It is preferred that the polyolefin bepresent in an amount from about 10 to about 50 parts by weight becausethis gives a very soft product that is usually desired for theapplication.

It is very common that such compositions contain filler materials suchas mica, calcium carbonate, talc, wollastonite, etc. in order to bringdown the cost of the composition and, when not present in large amounts,improve moldability. In the present situation, no more than about 20% ofthe composition should be comprised of a filler because if more thanthat amount is used, then the composition will not be sufficiently softfor the intended use. Accordingly, it is preferred that the fillercomprise than less than about 10% of the total composition. However,there is some advantage to having the filler present in that it assistsin making the polymer sufficiently processable and prevents "blocking"of the ingredients during manufacture.

The polymer composition of the present invention is relatively soft andpaintable and can be injection molded to produce solid parts which arerelatively soft and can be easily painted with polyurethane basedPaints. After injection molding, this composition has the advantage thatthe paint will not peel from the surface, the low temperaturebrittleness is very good and it will stick well when it is injectionmolded over polyolefin parts such as polypropylene parts. Thecomposition may be used in the production of refrigerator door handles,appliance handles, furniture arm rests, luggage, etc. - anything inwhich a soft surface which can be painted is important. However, theprimary intended use for this composition is in the manufacture ofautomobile interior parts having a soft surface by insert or coinjectionmolding the polymer against a relatively stiff thermoplastic, such aspolypropylene, to which the polymer composition will adhere or even toone to which it will not adhere if mechanical interlocks or surfacetreatments are used. It also is possible to insert mold the polymercomposition of the present invention to molded metal parts.

EXAMPLES

The base polymer for all of the polymer compositions utilized in theseexamples is KRATON® G1651 rubber. This is a high molecular weight SEBSblock copolymer. The aliphatic hydrocarbon processing oil was eitherPENRECO® 4434 oil or 4465 oil which are high molecular weight refinedmineral oils free of aromatics. The polypropylene used herein was apolypropylene homopolymer produced by Shell Oil Company except in twocases wherein HUNTSMAN 5520 polypropylene homopolymer was used.

In some cases, the functionalized block copolymer was KRATON® FG1901Xblock copolymer which is a low molecular weight SEBS block copolymergrafted with maleic anhydride (approximately 1.7%). In Table II, KRATON®G1726 and KRATON® G1657 polymers are two different low molecular weightdiblock/triblock block copolymers. Although these polymers are producedwithout maleation, they were maleated subsequently.

Table I gives the composition of three different paint test sampleswhich did not include any functionalized block copolymer. Table II givesthe composition of four different paint test samples which utilizedifferent functionalized block copolymers within the scope of thepresent invention.

                  TABLE I                                                         ______________________________________                                        COMPOSITION OF PAINT TEST SAMPLES                                             Sample #        HD-4262  HD-4277    HD-4278                                   ______________________________________                                        Ingredients                                                                   High Molecular Weight                                                                         31.8%    31.5%      31.5%                                     S-EB-S Block Copolymer                                                        (KRATON ® G1651)                                                          Low Molecular Weight                                                                          --       --         --                                        Functionalized                                                                S-EB-S Block Copolymer                                                        (KRATON ® FG1901X)                                                        Polypropylene    4.5%     4.5%       4.5%                                     (HUNTSMAN 5520)                                                               Aliphatic Hydrocarbon                                                                         --       --           63%                                     Processing Oil                                                                (PENRECO ® 4434)                                                          Aliphatic Hydrocarbon                                                                           63%      63%      --                                        Processing Oil*                                                               (PENRECO ® 4465)                                                          Stabilizers     --         1%         1%                                      ______________________________________                                         *Special Low Volatility Type                                             

                  TABLE II                                                        ______________________________________                                        COMPOSITION OF PAINT TEST SAMPLES                                                                                 HD-4361                                                                       and                                       Sample #          HD-4363  HA-4388  HD-4362                                   ______________________________________                                        Ingredients                                                                   High Molecular Weight                                                                            24%      20%       6%                                      S-EB-S Block Copolymer                                                        (KRATON ® G1651 Rubber)                                                   Low Molecular Weight                                                                            --       --         6%                                      Functionalized                                                                S-EB-S Block Copolymer                                                        (KRATON ® FG1901X                                                         Rubber)*                                                                      Low Molecular Weight                                                                              6%     --       --                                        Functionalized S-EB/S-EB-S                                                    Experimental Block Copolymer                                                  (1726) (About 1.7% maleation)**                                               Low Molecular Weight                                                                            --        10%     --                                        Functionalized S-EB/S-EB-S                                                    Experimental Block Copolymer                                                  (1657) (About 1.0% malea-                                                     tion)***                                                                      Polypropylene     4.5%     4.5%     4.5%                                      (SHELL)                                                                       Aliphatic Hydrocarbon                                                                            60%      60%      60%                                      Processing Oil                                                                (PENRECO ® 4434)                                                          Stabilizers         1%       1%       1%                                      Calcium Carbonate 4.5%     4.5%     4.5%                                      Dusting Agent                                                                 ______________________________________                                         All these pelletized products were also dusted with HYSIL 233, an             amorphous silica.                                                             *FG1901X rubber was finely ground for HD4262 and unground for HD4361.         **Maleated G1726 rubber                                                       ***Maleated G1657 rubber                                                 

All of these paint test samples were injection molded onto apolypropylene injection molded part and then painted with a polyurethanebased paint. All of these polymers produced soft surfaces. In order totest the paintability, the painted surfaces of the molded parts were cutwith a razor blade to give an X cut, and the ability of the paint toresist being peeled away from the intersection point of the X wasassessed. The paint test samples which contain no functionalized blockcopolymer (HD-4262, 4277 and 4278) showed poor adhesion of the paint tothe polymer without the use of a tie coat. The paint samples whichutilize the functionalized block copolymer showed better paint adhesionwithout the use of a tie coat. The compositions which utilized KRATON®FG1901X rubber (HD-4361 and 4362) were superior to the compositionswhich utilized the other functionalized block copolymers (HD-4363 and4388).

We claim:
 1. A soft paintable polymer composition consisting essentiallyof:(a) from about 50 to about 90 parts by weight (pbw) of a hydrogenatedblock copolymer comprised of at least one vinyl aromatic hydrocarbon andat least one conjugated diene, (b) from about 10 to about 50 pbw of afunctionalized hydrogenated block copolymer comprised of at least onevinyl aromatic hydrocarbon and at least one conjugated diene, wherein(a) and (b) must add up to 100 pbw, (c) from about 50 to about 300 pbwof a predominantly aliphatic hydrocarbon processing oil, and (d) fromabout 5 to about 150 pbw of polypropylene.
 2. The polymer composition ofclaim 1 wherein the oil is present in an amount from about 150 to about250 pbw and the polypropylene is present in an amount from about 10 toabout 50 pbw.
 3. The polymer composition of claim 2 which also comprisesup to about 20% weight of a filler.
 4. The polymer composition of claim3 which contains not more that 10% weight of a filler.
 5. The polymercomposition of claim 1 wherein the block copolymer is functionalized bygrafting at least one acid or anhydride group or a derivative thereofonto a conjugated diene block.
 6. The polymer composition of claim 5wherein the acid or anhydride group or derivative thereof is selectedfrom the group consisting of mono- and polycarboxylic-containing acids,anhydrides and derivatives thereof.
 7. The polymer composition of claim6 wherein the acid or anhydride group or derivative group thereof ismaleic anhydride.
 8. The polymer composition of claim 7 wherein the oilis present in an amount from about 150 to about 250 pbw and thepolypropylene is present in an amount from about 10 to about 50 pbw. 9.A process for making a soft paintable molded product which comprises:(a)making a polymer composition consisting essentially of:(1) from about 50to about 90 parts by weight (pbw) of a hydrogenated block copolymercomprised of at least one vinyl aromatic hydrocarbon and at least oneconjugated diene, (2) from about 10 to about 50 pbw of a functionalizedhydrogenated block copolymer comprised of at least one vinyl aromatichydrocarbon and at least one conjugated diene, wherein (a) and (b) mustadd up to 100 pbw, (3) from about 50 to about 300 pbw of a predominantlyaliphatic hydrocarbon processing oil, and (4) from about 5 to about 150pbw of polypropylene; and (b) forming the composition into a moldedproduct.
 10. The polymer composition of claim 9 wherein the oil ispresent in an amount from about 150 to about 250 pbw and thepolypropylene is present in an amount from about 10 to about 50 pbw. 11.The polymer composition of claim 10 which also comprises up to about 20%by weight of a filler.
 12. The polymer composition of claim 11 whichcontains not more than 10% by weight of a filler.
 13. The polymercomposition of claim 9 wherein the block copolymer is functionalized bygrafting at least one acid or anhydride group or a derivative thereofonto a conjugated diene block.
 14. The polymer composition of claim 13wherein the acid or anhydride group or derivative thereof is selectedfrom the group consisting of mono- and polycarboxylic-containing acids,anhydrides and derivatives thereof.
 15. The polymer composition of claim14 wherein the acid or anhydride group or derivative group thereof ismaleic anhydride.
 16. The polymer composition of claim 15 wherein theoil is present in an amount from about 150 to about 250 pbw and thepolypropylene is present in an amount from about 10 to about 50 pbw.